When an organofunctionalized organopolysiloxane is copolymerized with organic resin monomer or is kneaded (i.e., blended) with an organic resin, the organic resin obtained will have excellent weather resistance, surface water repellency, lubricity, biocompatibility, gas permeability, and so forth. As a result, organofunctionalized organopolysiloxane is employed as an improver or modifier for organic resins.
Various types of organofunctionalized organopolysiloxanes are known for use as organic resin modifiers. Examples of these organofunctionalized organopolysiloxanes are amino modified organopolysiloxanes, epoxy-modified organopolysiloxanes, methacryloxy-modified organopolysiloxanes, carbinol-modified organopolysiloxanes and carboxylic acid-modified organopolysiloxanes. These organofunctionalized organopolysiloxanes are typically prepared by a platinum-catalyzed hydrosilylation reaction between SiH-containing organopolysiloxane and an organofunctional group-containing, aliphatically unsaturated hydrocarbon. Methylpolysiloxane customarily makes up the basic skeleton of the SiH-containing organopolysiloxanes used in this preparative scheme.
Within the context of application as an improver or modifier for organic resins, phenyl containing organopolysiloxanes have a better affinity for organic resins than do methyl-containing organopolysiloxanes. In addition, when an organic resin is kneaded with phenyl-containing organopolysiloxane, the resulting organic resin will have an excellent radiation resistance, heat resistance, noncombustibility, and low-temperature flexibility.
Thus, phenyl-containing organofunctionalized organopolysiloxanes are highly desirable as modifiers or improvers for organic resins for the purpose of improving various properties of these organic resins. The starting material for such phenyl-containing organofunctionalized organopolysiloxanes is a (phenyl+SiH)-containing organopolysiloxane. However, this starting material is extremely difficult to prepare. Cleavage of the silicon-phenyl bond occurs when the (phenyl+SiH)-containing organopolysiloxane is prepared by an equilibration polymerization reaction in the presence of an acid catalyst, while cleavage of the silicon-hydrogen bond occurs when it is prepared by an equilibration polymerization reaction in the presence of a basic catalyst.
The present inventor has already proposed a diphenylsiloxane-dimethylsiloxane copolymer bearing SiH at only one molecular chain terminal or at both molecular chain terminals, as well as methods for the preparation of same: Japanese Patent Application Numbers 02-114177 (114,177/90) and 02-336315 (336,315/90).
The preparative methods proposed in Japanese Patent Application Numbers 02-114177 and 02-336315 characteristically afford a diphenylsiloxane-dimethylsiloxane copolymer bearing SiH at only one molecular chain terminal or at both molecular chain terminals in high yields, which copolymer has a narrow molecular weight distribution. Nevertheless, these methods suffer from certain problems. Thus, expensive, difficult-to-handle organolithium compounds are employed. Moreover it is difficult to control the polymerization reaction organopolysiloxanes having side-chain SiH cannot be prepared and organopolysiloxane having high SiH contents cannot be prepared.